Electronically deriving a conclusion of the condition of slurry flow in a non-vertical conduit

ABSTRACT

A method of electronically deriving a conclusion of a condition of slurry flow in a non-vertical conduit having a conduit wall and which contains a slurry to flow or flowing along the conduit is provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/512,380, filed on Mar. 17, 2017, which claims priority toInternational Application No. PCT/ZA2015/050010, filed on Sep. 18, 2015,and South African Patent Application No. 2014/06834, filed on Sep. 18,2014. The entire contents of each of the foregoing applications areincorporated herein by reference.

FIELD OF THE INVENTION

THIS INVENTION provides for electronically deriving a conclusion of thecondition of slurry flow in a conduit. The invention provides a methodof electronically deriving a conclusion of the condition of slurry flowin a non-vertical conduit. The invention also provides a system forelectronically deriving a conclusion of the condition of slurry flow ina non-vertical conduit.

BACKGROUND TO THE INVENTION

IN THIS SPECIFICATION the term “slurry” refers broadly to mixtures ofsolids and liquids. This includes aqueous mixtures, in thickened orun-thickened form. Such mixtures may, for example, be in the form oftailings, concentrates, pastes, sludges (which may include biologicallyactive solid ingredients), industrial wastes, or oil sands. “Slurry”particularly includes slurries that are regarded as “settling slurries”.A “settling slurry” is a slurry that has a tendency to deposit, throughgravity, a sediment or settled particle bed when flowing at a velocityslower than a “critical deposition velocity” of the slurry.

It is well established that a slurry is pumped most economically at avelocity just above its critical deposition velocity. The criticaldeposition velocity varies from case to case and is dependent on anumber of different factors. Such factors include solids concentrationor density of the slurry, composition of the slurry, particle sizedistribution in the slurry, and so on. In the mining and mineralextraction industry, as an example, thickened slurries or tailings arepumped through pipelines from mineral extraction plants to tailingsdams. At velocities below the critical deposition velocity, solidparticles in the slurry tend to settle in the pipeline, forming asliding or stationary settled particle bed at the invert of thepipeline. This has a negative effect on pumping velocity at constantpumping power, and continuing build-up of sediment could eventually leadto pipeline blockage. If the slurry contains larger particles, suchparticles will tend to settle out first. This may lead to undesired,unstable operating conditions.

It seems obvious that to avoid negative consequences associated withpumping below the critical deposition velocity, pumping should beeffected well in excess of it. However, this will increase operatingcosts, since more power will be consumed and since there will be greaterfrictional losses and pipeline wear. Another seemingly obvious measureis to reduce the particle concentration or density of the slurry byincreasing the water content in order to decrease the criticaldeposition velocity. However, this may be an undesirable wastage ofwater and/or require an additional pumping operation to pump excesswater back from the disposal site.

Even if, as is conventionally the case, slurry pumping systems aredesigned to operate above the critical deposition velocity determinedfor a particular slurry, it must be appreciated that the actualproperties of the slurry may vary considerably from time to time. Thisis particularly so with respect to the ultrafine content in the particlesize distribution of the slurry, the maximum particle size and themineral composition. Selecting a single operating power with a safetymargin worked in is therefore non-ideal over this variability. It wouldbe more beneficial proverbially to sail closer to the wind, to detectthe onset of particle settlement by means of instrumentation, and thento control the flow velocity continuously and maintain it at the lowestvalue possible while the concentration of the slurry is maintained at anappropriately high value. The present invention seeks to allow forachieving such control.

SUMMARY OF THE INVENTION

THE ANGULAR SPACINGS that are referred to in this specification areabout an axis extending along a cross-sectional centre of a normal levelof flow in the conduit that is provided. It will be appreciated thatwhen the normal level of flow in the conduit is at a level at which theconduit is cross-sectionally filled with slurry, this centre will be ageometric cross sectional centre of the conduit.

Furthermore, the expression “condition of slurry flow” used in thisspecification is regarded as including a condition in which slurry flowsalong the conduit, but a settled particle bed has formed inside theconduit at the invert of the conduit. Therefore, the formation of asettled particle bed inside the conduit at the invert of the conduit isregarded as being part of the concept of “condition of slurry flow”. Theconcept is also regarded as including a condition in which the conduitcontains slurry, but in which there is virtually no flow of the slurryin the conduit.

In some embodiments there is provided a method of deriving a conclusionof the condition of slurry flow in a non-vertical conduit having aconduit wall, the method including

-   -   generating, at a first heating point along the conduit wall        which is at the invert of the conduit, a first locally heated        spot on an interior surface of the conduit wall by means of heat        delivered to the conduit wall at a heating power level that is        maintained substantially over time;    -   generating, at a second heating point along the conduit wall        that is angularly spaced from the first heating point at an        angular spacing of at least 90°, a second locally heated spot on        the interior surface of the conduit wall by means of heat        delivered to the conduit wall at a heating power level that is        also maintained substantially constant over time;    -   locally measuring the temperatures of the first and second        heated spots respectively, thereby obtaining first and second        temperature values T1 and T2;    -   optionally measuring, at a reference point, a reference        temperature and thereby obtaining a reference temperature value        T3; and    -   deriving a conclusion of slurry flow conditions prevailing in        the conduit from at least one temperature difference selected        from a first temperature difference, which is T1 minus T2, and a        second temperature difference, which is T2 minus T3.

In some embodiments, the optional step is carried out.

In some embodiments, there is provided a system for deriving aconclusion of the condition of slurry flow in a non-vertical conduithaving a conduit wall, the system including

-   -   at least one heat source mounted to deliver heat to the conduit        wall at        -   a first heating point along the wall which is at the invert            of the conduit, thereby to generate, in use, a first locally            heated spot on an interior surface of the conduit wall by            means of heat delivered to the conduit wall; and        -   a second heating point along the wall which is angularly            spaced from the first heating point at an angular spacing of            at least 90°, thereby to generate, in use, a second locally            heated spot on an interior surface of the conduit wall by            means of heat delivered to the conduit wall,            the system further including    -   first and second temperature sensors that are arranged to        measure, in use, the temperatures of the first and second heated        spots respectively, thereby to obtain first and second        temperature values T1 and T2;    -   optionally, a reference temperature sensor that is arranged at a        reference point to measure, in use, a reference temperature and        obtain a reference temperature value T3; and    -   a computing device in communication with the first and second        temperature sensors, and with the reference temperature sensor        when provided, the computing device being programmed to derive        an indication of slurry flow conditions prevailing in the        conduit from at least one temperature difference selected from a        first temperature difference, which is T1 minus T2, and a second        temperature difference, which is T2 minus T3, which temperature        differences the computing device is programmed to calculate.

In some embodiments, the reference temperature sensor is provided.

In some embodiments, there is provided a method of electronicallyderiving a conclusion of the condition of slurry flow in a non-verticalconduit having a conduit wall and which contains a slurry to flow orflowing along the conduit, the method including

-   -   artificially generating at a first heating point along the        conduit wall, which is defined at the invert of the conduit, a        first locally heated spot on an interior surface of the conduit        wall by means of heat delivered to the conduit wall by a heating        device at a first heating power level that is maintained        substantially constant over time;    -   artificially generating at a second heating point along the        conduit wall, which is defined angularly spaced from the first        heating point at an angular spacing of at least 90°, a second        locally heated spot on the interior surface of the conduit wall        by means of heat delivered to the conduit wall by a heating        device at a second heating power level that is also        substantially constant over time;    -   locally measuring the temperatures of the first and second        locally heated spots respectively, thereby obtaining first and        second temperature values (respectively T1 and T2);    -   communicating electronically generated signals carrying the        values T1 and T2 to an electronic computing device, which        operatively receives the signals and electronically        -   automatically calculates a first temperature difference T1            minus T2; and        -   automatically derives a conclusion of the condition of            slurry flow prevailing in the conduit based at least on the            relationship between the value of the first temperature            difference and a first reference parameter, which is a            reference parameter for the first temperature difference.

By “operatively receives” is meant that the computing device receivesthe signals carrying the values of T1 and T2, and interprets or decodesthe signals in whichever manner necessary in order to calculate thefirst temperature difference. With respect to the signals it will beappreciated that embodiments can exist in which a single combined signalis communicated, rather than respective signals.

In some embodiments, heating supplied by all heating devices createsheated spots that would be, at least when there is no slurry flow in thepipe, at temperatures above the temperature of the slurry.

The method may also include

-   -   measuring, at a predetermined reference point spaced from the        first and second heating points, a third, reference temperature        and thereby obtaining a third, reference temperature value (T3);        and    -   communicating an electronically generated signal carrying the        value T3 to the electronic computing device, which operatively        receives the signal and automatically calculates a second        temperature difference T2 minus T3,        wherein automatically deriving a conclusion, by means of the        computing device, of the condition of slurry flow prevailing in        the conduit is based also on the relationship between the value        of the second temperature difference or of T2 and a second        reference parameter, which is a reference parameter for the        second temperature difference or for T2.

The reference point would typically be selected for minimal or nointerference of the heated spots with the reference temperature.Accordingly, the reference point is preferably a point which is spacedas far away from the first and second heating points as possible,observing any desired restrictions on its location. The reference pointneed not be on the conduit, but preferably it is on the conduit as isstated below in greater detail.

The second reference parameter may be a predetermined threshold valuefor the second temperature difference. For example, the second referenceparameter may be predetermined at 8° C., thus requiring the secondtemperature difference to be, at most, 8° C.

The method may then include

-   -   automatically comparing, by means of the computing device, the        second temperature difference to the second reference parameter;        and    -   automatically concluding, by means of the computing device, that        the condition of slurry flow in the conduit is that there is no        flow in the conduit, on the basis that the second temperature        difference exceeds the second reference parameter.

Alternatively, the second reference parameter may be a threshold valuefor T2 and may be calculated as a predetermined value above the measuredvalue for T3. For example, the predetermined value above the measuredvalue of T3 may be 8° C. Therefore, the second reference parameter maybe T3 plus 8° C.

The method may then include

-   -   automatically comparing, by means of the computing device, T2 to        the second reference parameter; and    -   automatically concluding that the condition of slurry flow in        the conduit is that there is no flow in the conduit, on the        basis that T2 exceeds the second reference parameter.

Alternatively, the second reference parameter may be a predeterminedundesired change in the second temperature difference over apredetermined time period. The method may then include

-   -   automatically noting, by means of the computing device, changes        in the second temperature difference; and    -   automatically concluding that the condition of slurry flow in        the conduit is that there is no flow in the conduit, on the        basis that a change in the second temperature difference over        the predetermined time period is equal to, or exceeds the        predetermined undesired change over the predetermined time        period.

The predetermined undesired change in the second temperature differencemay, for example, be 0.25° C., while the predetermined time period may,for example, be 10 seconds.

The conclusion derived on the basis of the second temperature differencethat there is no flow in the conduit, may override any conclusionderived on the basis of the first temperature difference. “Override” inthis specification means that a particular conclusion, whether it is theconclusion drawn on the basis of the first temperature difference, thesecond temperature difference, or any of the other temperaturedifferences referred to below, is an “output conclusion”, or “rulingconclusion”. In one sense, the output conclusion is the conclusion orgroup of conclusions on the basis of which the electronic response/shereinafter described is/are provided.

The method may include noting, as a threshold value, the value of T2minus T3 (i.e. the second temperature difference) when the conclusionthat there is no flow in the conduit has been derived. The conclusionthat there is no flow in the conduit may then continue to override anyconclusion derived on the basis of the first temperature difference,until the value of T2 minus T3 is below the noted threshold value for T2minus T3.

Alternatively, the method may include comparing the value of T2 minus T3(i.e. the second temperature difference) to a threshold value to derivea conclusion that there is no flow in the conduit. The conclusion thatthere is no flow in the conduit may then continue to override anyconclusion derived on the basis of the first temperature difference,until the value of T2 minus T3 is below the noted threshold value for T2minus T3.

The method may further include

-   -   artificially generating at a third heating point along the        conduit wall, which is defined between the first heating point        and the second heating point at an angular spacing of less than        90° from the first heating point about the longitudinal axis, a        third locally heated spot on the interior surface of the conduit        wall, by means of heat delivered to the conduit wall by a        heating device at a third heating power level that is maintained        substantially constant over time;    -   locally measuring the temperature of the third heated spot and        thereby obtaining a fourth temperature value T4;    -   communicating an electronically generated signal carrying the        value T4 to the computing device, which electronically        -   automatically calculates a third temperature difference T4            minus T2; and        -   automatically derives a conclusion of the condition of            slurry flow prevailing in the conduit at the third heated            spot, based on the relationship between the value of the            third temperature difference and a third reference            parameter, which is a reference parameter for the third            temperature difference.

The steps outlined in the preceding paragraph may be carried out inrespect of fourth and, optionally, further heating points along theconduit wall, defined between the first and second heating points. Inother words, fourth and, optionally, further locally heated spots may begenerated on the interior surface of the conduit. The method may theninclude

-   -   obtaining fifth and, optionally, further temperature values T5 .        . . Tn by local measurement of the temperatures of the fourth        and optional further heated spots;    -   communicating (an) electronically generated signal/s carrying        the value/s T5 . . . Tn to the computing device, which        electronically        -   automatically calculates fourth and, optionally, further            temperature differences T5 minus T2 . . . Tn minus T2; and        -   automatically derives one or more further conclusions of the            conditions of slurry flow prevailing in the conduit at the            fourth and optional further heated spots, based on the            relationship between the value/s of the fourth and optional            further temperature differences and fourth and optional            further reference parameter/s, which is/are (a) reference            parameter/s for each of the fourth and optional further            temperature differences respectively.

Each of the first, third, fourth and optional further referenceparameters, when employed, may be a predetermined desired value of eachof the first, third, fourth and optional further temperaturedifferences. The method may then include concluding, by means of thecomputing device, that the condition of slurry flow in the conduit isthat a settled particle bed has formed inside the conduit at one or moreof the first, third, fourth and optional further heated spots on thebasis that, respectively, one or more of the first, third fourth andoptional further temperature differences is/are greater than theirrespective predetermined desired values, optionally greater thanpredetermined standard allowable deviations from their respectivepredetermined desired values. Preferably, the predetermined desiredvalue of each of the first, third, fourth and optional furthertemperature differences is 0 (zero).

Any conclusion derived on the basis of each of the first, third, fourthand optional further temperature differences may override any conclusionderived on the basis of the second temperature difference, and thereforebe the output conclusion or provide a group of output conclusions, untilany change noted in the second temperature difference over thepredetermined time period is equal to, or exceeds the predeterminedundesired change over the predetermined time period. At such a time, theconclusion derived on the basis of the second temperature differencewill become the output conclusion.

Measuring the temperatures of the respective heated spots may beeffected independently of the heating devices that provide therespective heating spots.

The method may include providing or causing, by means or under directionof the computing device, an electronic response to at least thefollowing conclusions, when derived by the computing device in themanner hereinbefore described:

-   -   that there is no flow in the conduit; and    -   that a settled particle bed has formed in the conduit at the        locally heated spot from which the temperature value that is        used to calculate the temperature difference on the basis of        which the conclusion of the formation of a settled particle bed        is derived, is obtained.

In other words, for the latter conclusion, respective electronicresponses may be provided for respective conclusions that settled bedshave formed at the first, third, fourth and optional further heatedspots respectively. It will be appreciated that settled beds forming atthe third, fourth and optional further heated spots are dependent on theformation of a settled bed at the first heated spot, taking into accountthat the formation of settled beds at the third, fourth and optionalfurther heated spots requires the formation of a settled bed at thefirst heated spot, at least in the preferred configuration of locationsof the first, second, third, fourth and optional further heated pointsas discussed below.

The electronic response may be or cause a visual and/or audio indicationthat the conclusion causing the electronic response has been derived bythe computing device. Visual indications may include warning lights.Visual indications may also include text or graphic representations on acomputer screen or other electronic display.

It must be appreciated that conclusions derived of the conditions ofslurry flow prevailing in the conduit at the third, fourth and optionalfurther heated spots provides an indication of the profile of a settledbed that may have formed in the conduit. Thus, if the conclusionsderived from the first and third temperature differences are thatsettled beds have formed at the first and third heated spots, but theconclusion derived from the fourth temperature difference is not that asettled bed has formed at the fourth heated spot, an indication isobtained that the depth of the settled particle bed is only up to thethird heated spot.

The reference point, when defined, may be defined on the conduit wall.The reference temperature may therefore be a temperature of the conduitwall. Preferably, no artificial heating is supplied at the referencepoint.

The spacings between the reference point, the first, second, third,fourth and the optionally further heating points, whichever are defined,are preferably only angular, not longitudinal or axial along theconduit. In other words, the reference point and all of the heatingpoints preferably all lie in the same cross sectional plane of theconduit. The angular spacing between the first and second heating pointsis preferably 120°. In such a case, when the reference point is definedon the conduit, the first, second and reference points are preferablyequiangularly spaced from each other, i.e. at angular spacings of 120°.The third, fourth and optional further heating points preferably all lieon the same side between the first and second heating points. This sideis preferably the side of smallest angular spacing between the first andsecond heating points.

The temperature of each heated spot may be locally measured at itsheating point. Measurement may, in particular, be effected insubstantially the same plane in which each heating point and heatingspot is located. Alternatively, measurement may be effected in a planeslightly upstream of the plane is which the heating point and heatingspot is located, e.g. 15 mm upstream therefrom. It will be appreciatedthat this may, however, still be regarded as effectively being in the“same plane”, depending on how thick the plane is regarded to be. Thereference temperature may be measured at the reference point.

The heating power level/s of the heating device/s may be selected withreference to the reference temperature, such that the actualtemperature/s of working surface/s of the heating device/s is/are, ineach case, higher than the reference temperature. Preferably, the actualtemperature/s of working surface/s of the heating device/s is/are, ineach case, about 5° C. to about 10° C. higher than the referencetemperature. In this regard, the term “working surface” refers to asurface of the heat source that is in contact with the conduit wall,typically on an outside thereof, to deliver heat to the interior of theconduit wall by conductive heat transfer.

The heating power levels of all of the heating devices are preferablyequal, such that the actual temperatures of the respective workingsurfaces are also equal, at least at full flow.

The conduit may be substantially horizontal. It is well established thata conduit, or pipe, inclination of 30 degrees to the horizontal requiresa higher velocity to prevent particle settling than a horizontalconduit, or pipe.

The conduit may be a pipe. Typically, the pipe may have a wall thicknessof about 2 to about 20 mm.

In some embodiments, there is provided a slurry flow conditionmonitoring system for electronically deriving a conclusion of thecondition of slurry flow in a non-vertical conduit having a conduit walland which contains a slurry to flow or flowing along the conduit, thesystem including

-   -   at least one heating device that is arranged to deliver heat to        the conduit wall at        -   a first heating point along the conduit wall, which is            defined at the invert of the conduit, thereby artificially            to generate, in use, a first locally heated spot on an            interior surface of the conduit wall by delivering heat to            the conduit wall at a first heating power level that is            maintained substantially constant over time; and        -   a second heating point along the conduit wall, which is            defined angularly spaced from the first heating point at an            angular spacing of at least 900, thereby artificially to            generate, in use, a second locally heated spot on an            interior surface of the conduit wall by delivering heat to            the conduit wall at a second heating power level that is            substantially constant over time,            the system further including    -   first and second temperature sensors that are arranged locally        to measure, in use, the temperatures of the first and second        heated spots respectively, thereby to obtain first and second        temperature values (respectively T1 and T2);    -   electronic signal generating means capable of electronically        generating, in use, signals carrying the values T1 and T2; and    -   a computing device that is in communication with the electronic        signal generating means operatively to receive the signals        carrying the values T1 and T2, the computing device being        programmed electronically        -   to automatically calculate a first temperature difference T1            minus T2; and        -   to automatically derive a conclusion of slurry flow            conditions prevailing in the conduit, based at least on the            relationship between the value of the first temperature            difference and a first reference parameter, which is a            reference parameter for the first temperature difference.

The system may be a system for implementing the method of the invention.Accordingly, parts of the system may be such that they are capable ofimplementing the method of the invention, therefore havingfunctionalities corresponding to the steps and features of the methodhereinbefore described.

The system may include

-   -   a third temperature sensor that is arranged to measure a third,        reference temperature at a reference point spaced from the first        and second heating points, thereby to obtain a third, reference        temperature value (T3); and    -   electronic signal generating means capable of electronically        generating, in use, a signal carrying the value T3,        wherein the computing device is in communication with the        electronic signal generating means operatively to receive the        signal carrying the value T3 and is programmed electronically    -   to automatically calculate a second temperature difference T3        minus T2; and    -   to automatically derive a conclusion of slurry flow conditions        prevailing in the conduit based also on the relationship between        the value of the second temperature difference or of T2 and a        second reference parameter, which is a reference parameter for        the second temperature difference or for T2.

The second reference parameter may be a predetermined threshold valuefor the second temperature difference. For example, the second referenceparameter may be predetermined at 8° C., thus requiring the secondtemperature difference to be, at most, 8° C.

The computing device may then be programmed electronically to

-   -   automatically compare, by means of the computing device, the        second temperature difference to the second reference parameter;        and    -   automatically conclude, by means of the computing device, that        the condition of slurry flow in the conduit is that there is no        flow in the conduit, on the basis that the second temperature        difference exceeds the second reference parameter.

Alternatively, the second reference parameter may be a threshold valuefor T2 and may be calculated as a predetermined value above the measuredvalue for T3. For example, the predetermined value above the measuredvalue of T3 may be 8° C. Therefore, the second reference parameter maybe T3 plus 8° C.

The computing device may then be programmed electronically to

-   -   automatically compare, by means of the computing device, T2 to        the second reference parameter; and    -   automatically conclude that the condition of slurry flow in the        conduit is that there is no flow in the conduit, on the basis        that T2 exceeds the second reference parameter.

Alternatively second reference parameter may be a predeterminedundesired change in the second temperature difference over apredetermined time period. In such a case the computing device may beprogrammed electronically

-   -   to automatically note changes in the second temperature        difference; and    -   to automatically conclude that the condition of slurry flow in        the conduit is that there is no flow in the conduit, on the        basis that a change in the second temperature difference over        the predetermined time period is equal to, or exceeds the        predetermined undesired change over the predetermined time        period.

The computing device may be programmed such that the conclusion derivedon the basis of the second temperature difference that there is no flowin the conduit, overrides any conclusion derived on the basis of thefirst temperature difference.

The computing device may be electronically programmed automatically touse a threshold value for the value of T2 minus T3 to derive at aconclusion that there is no flow in the conduit. The computing devicemay also be programmed such that the conclusion derived on the basis ofthe second temperature difference that there is no flow in the conduit,continues to override any conclusion drawn on the basis of the firsttemperature difference until the value of T2 minus T3 is below thethreshold value of T2 minus T3.

The system may also include

-   -   a heating device arranged to deliver heat to the conduit wall at        a third heating point along the conduit wall, which is defined        between the first heating point and the second heating point at        an angular spacing of less than 90° from the first heating        point, thereby artificially to generate a third locally heated        spot on the interior surface of the conduit wall at a third        heating power level that is maintained substantially constant        over time;    -   a fourth temperature sensor that is arranged locally to measure,        in use, the temperature of the third heated spot, thereby to        obtain a fourth temperature value (T4);    -   electronic signal generating means capable of electronically        generating, in use, a signal carrying the value T4 and of        communicating the signal to the computing device, the computing        device being in communication with the electronic signal        generating means operatively to receive the electronically        generated signal carrying the value T4 and being programmed        electronically        -   to automatically calculate a third temperature difference T4            minus T2; and        -   to automatically derive a conclusion of slurry flow            conditions prevailing in the conduit at the third heated            spot, based at least on the relationship between the value            of the third temperature difference and a third reference            parameter, which is a reference parameter for the third            temperature difference.

Furthermore, the system may also include

-   -   one or more heating devices arranged to deliver, at heating        levels that are maintained constant over time, heat to the        conduit wall at fourth and, optionally, further heating points        along the conduit wall, between the first heating point and the        second heating point, thereby artificially to generate fourth        and, optionally, further locally heated spots on the interior        surface of the conduit;    -   one or more temperature sensors arranged locally to measure, in        use, the temperatures of the fourth and optionally further        heated spots respectively, thereby to obtain fifth and,        optionally, further temperature values (T5 . . . Tn);    -   electronic signal generating means capable of electronically        generating, in use, (a) signal/s carrying the value/s T5 . . .        Tn and of communicating the signal/s to the computing device,        the computing device being in communication with the electronic        signal generating means operatively to receive the        electronically generated signal/s carrying the value/s T5 . . .        Tn and being programmed electronically        -   to automatically calculate fourth and optionally further            temperature difference/s T5 minus T2 . . . Tn minus T2; and        -   to automatically derive a conclusion of slurry flow            conditions prevailing in the conduit at the fourth and            optionally further heated spot/s, based at least on the            relationship between the value of (a) fourth and optionally            further temperature difference/s and (a) fourth and            optionally further reference parameter/s, which is/are a            reference parameter/s for the fourth and optionally further            temperature difference/s respectively.

Each of the first, third, fourth and optional further referenceparameters, when employed, may be a predetermined desired value of eachof the first, third, fourth and optional further temperaturedifferences. The computing device may be programmed electronically toconclude that the condition of slurry flow in the conduit is that asettled particle bed has formed inside the conduit at one or more of thefirst, third, fourth and optional further heated spots on the basisthat, respectively, one or more of the first, third fourth and optionalfurther temperature differences is/are greater than their respectivepredetermined desired values, optionally greater than predeterminedstandard allowable deviations from their respective predetermineddesired values. Preferably, the predetermined desired value of each ofthe first, third, fourth and optional further temperature differences is0 (zero).

The computing means may be programmed such that any conclusion derivedon the basis of each of the first, third, fourth and optional furthertemperature differences overrides any conclusion derived on the basis ofthe second temperature difference, until any change noted in the secondtemperature difference over the predetermined time period is equal to,or exceeds the predetermined undesired change over the predeterminedtime period.

The computing means may be programmed to provide or cause an electronicresponse to at least the following conclusions, when derived by thecomputing device:

-   -   that there is no flow in the conduit; and    -   that a settled particle bed has formed in the conduit at the        locally heated spot from which the temperature value that is        used to calculate the temperature difference on the basis of        which the conclusion of the formation of a settled particle bed        is derived, is obtained.

The system may include audio and/or visual indicating means. Theelectronic response may be or cause the indicating means to provide avisual and/or audio indication that the conclusion causing theelectronic response has been derived by the computing device. Visualindicating means may include warning lights. Visual indicating means mayalso refer to computer screens, on which text or graphic representationsare provided as indications screens.

The first and second heating points may both lie in the samecross-sectional plane of the conduit. The reference point, when defined,may be defined on the conduit wall and may also lie in the samecross-sectional plane as the first and second heating points. The third,fourth and further heating points (when defined) may also lie in thesame cross-sectional plane as the first and second heating points.

In some embodiments, there is provided method of electronically derivinga conclusion of the condition of slurry flow in a non-vertical conduithaving a conduit wall and which contains a slurry to flow or flowingalong the conduit, the method including

-   -   artificially generating at a first heating point along the        conduit wall, which is defined at the invert of the conduit, a        first locally heated spot on an interior surface of the conduit        wall, by means of heat delivered to the conduit wall by a        heating device at a first heating power level W1;    -   artificially generating at a second heating point along the        conduit wall, which is defined angularly spaced from the first        heating point at an angular spacing of at least 90°, a second        locally heated spot on the interior surface of the conduit wall        by means of heat delivered to the conduit wall by a heating        device at a second heating power level W2,        one of the heating power levels W1, W2 being substantially        constant over time,    -   locally measuring the temperatures of the first and second        locally heated spots respectively, thereby obtaining first and        second temperature values (respectively T1 and T2);    -   communicating electronically generated signals carrying the        values T1 and T2 to an electronic computing device, which        operatively receives the signals and electronically        automatically calculates a first temperature difference T1 minus        T2; and    -   comparing, by means of the computing device, the first        temperature difference to a desired constant for the first        temperature difference;    -   selectively increasing or decreasing, by means of the computing        device, heat delivered to the heating device that does not        deliver constant heating power over time, to maintain the        desired constant for the first temperature difference; and    -   calculating, by means of the computing device, a first power        level difference W1 minus W2 and automatically deriving a        conclusion of the condition of slurry flow prevailing in the        conduit based at least on the relationship between the value of        the first power level difference and a first reference        parameter, which is a reference parameter for the first power        level difference.

Preferably W1 is constant and W2 is variable, and is varied as necessaryin accordance with the method, over time.

This embodiment is regarded as a less desirable embodiment. Theapplicant has noticed that with presently available equipment,undesirable delays occur in the response of heating devices to maintaina constant temperature difference. This results in inaccurateconclusions being derived of the condition of slurry flow in theconduit. Nevertheless, this embodiment is presented as a possiblealternative.

The desired constant for the first temperature difference may be thetemperature difference between the first and second heated spots whenthere is full flow in the conduit.

The method may include measuring a reference temperature T3, as in themethod hereinbefore described as the first aspect of the invention, andusing the reference temperature in the same manner hereinbeforedescribed to derive a conclusion of no flow in the conduit, while thefirst power difference is used to derive a conclusion of the formationof a settled particle bed in the conduit. The reference parameter forthe first power difference is, preferably, 0 (zero).

The method may also include employing third, optional fourth andoptional further heating devices, in the same manner described for thefirst aspect of the invention, thereby to generate third, optionalfourth and optional further heated spots with variable power delivery.The method may then include locally measuring third, optional fourth andoptional further temperatures of the third, optional fourth and optionalfurther heated spots, and calculating third, optional fourth andoptional further temperature differences T4 minus T2, T5 minus T2 . . .Tn minus T2. The method may then further include measuring third,optional fourth and optional further power levels W3, W4 . . . Wn andcalculating second, optional third and optional further power leveldifferences between W1 and W3, W1 and optional W4 . . . W1 and optionalWn, resulting when controlling W3, W4 . . . Wn to maintain third, fourthand optional further temperature differences T4 minus T2, T5 minus T2 .. . Tn minus T2 substantially constant and thereby to derive conclusionsof slurry flow conditions prevailing at other locations in the conduit,in the same cross sectional plane in which the first and second heatingdevices are located.

In some embodiments, there is provided a system for implementing themethod of the third aspect of the invention, including appropriateheating devices, temperature sensors and an appropriately programmedcomputing device.

In some embodiments, there is provided a method of electronicallyderiving a conclusion of a condition of slurry flow in a non-verticalconduit having a conduit wall and which contains a slurry to flow orflowing along the conduit, the method comprising:

-   -   artificially generating at a first heating point on the conduit        wall, which is defined at the invert of the conduit, a first        locally heated spot on an interior surface of the conduit wall,        using heat delivered to the conduit wall by a first heating        device at a first variable heating power level W1 that is        substantially constant over time;    -   artificially generating at a second heating point on the conduit        wall, which is defined angularly spaced from the first heating        point at an angular spacing of at least 900 and which is not        spaced from the first heating point along the length of the        conduit but which lies in the same cross-sectional plane of the        conduit as the first heating point, a second locally heated spot        on the interior surface of the conduit wall using heat delivered        to the conduit wall by a second heating device at a second        variable heating power level W2 that is substantially constant        over time;    -   locally measuring the temperatures of the first and second        locally heated spots respectively, thereby obtaining a first        temperature value T1 and a second temperature value T2;    -   measuring, at a predetermined reference point spaced from the        first and second heating points, a third reference temperature        value T3;    -   communicating electronically generated signals carrying the        values W1, W2, T1, T2, and T3 to one or more electronic        computing devices, which operatively receive/s the signals and        electronically:        -   automatically            -   calculate/s a first temperature difference dT1 between                T1 and T3 and compare/s dT1 to a reference value for                dT1, being dT1ref, or            -   compare/s T1 to a desired value for T1, being T3″ that                is T3 plus a predetermined value T3′,        -   automatically cause/s the first heating device to change the            heating power level W1 delivered to the conduit wall at the            first heating point if            -   dT1 is not equal to dT1ref, optionally not within an                allowable deviation of dT1ref, sufficiently to change T1                such that dT1 is equal to dT1ref, optionally within an                allowable deviation of dT1ref, or            -   T1 is not equal to T3″, optionally within an allowable                deviation of T3″, sufficiently to change T1 such that T1                is equal to T3″, optionally within an allowable                deviation of T3″ automatically            -   calculate/s a second temperature difference dT2 between                T2 and T3 and compare/s dT2 to a reference value for                dT2, being dT2ref, or            -   compare/s T2 to a desired value for T2, being T3″″ that                is T3 plus a predetermined value T3′″;        -   automatically cause/s the second heating device to change            the heating power level W2 delivered to the conduit wall at            the second heating point if            -   dT2 is not equal to dT2ref, optionally not within an                allowable deviation of dT2ref, sufficiently to change T2                such that dT2 is equal to dT2ref, optionally within an                allowable deviation of dT2ref, or;            -   T2 is not equal to T3″″, optionally within an allowable                deviation of T3″″, sufficiently to change T1 such that                T1 is equal to T3″″, optionally within an allowable                deviation of T3″″;        -   automatically calculate/s a power difference dW between W1            and W2 and compare/s dW to a reference value for dW, being            dWref;        -   automatically compare/s W2 to a reference value for W2,            being W2ref, and        -   automatically derive/s a conclusion of a condition of slurry            flow prevailing in the conduit based at least on a            relationship between dW and dWref and between W2 and W2ref,            that            -   if an absolute value of dW is smaller than an absolute                value of dWref and an absolute value of W2 is greater                than an absolute value of W2ref, there is unrestricted                flow in the conduit, in that no flow restricting bed of                solid material has formed at the invert of the conduit,            -   if an absolute value of dW is greater than an absolute                value of dWref and an absolute value of W2 is greater                than an absolute value of W2ref, there is partially                restricted flow in the conduit, in that a flow                restricting bed of solid material has formed at the                invert of the conduit, and            -   if an absolute value of W2 is smaller than an absolute                value of W2ref, there is restricted flow in the conduit,                in that flow in the conduit has virtually ceased.

That W1 and W2 are substantially constant over time would typicallyapply at unrestricted flow in the conduit, since W1 and W2 would bevaried when there is a change in flow conditions in the conduit inaccordance with the method of the invention.

One or more, or all, of the following conditions may typically apply toW2ref, dWref, W1 at unrestricted flow, and W2 at unrestricted flow:

-   -   W2ref>0    -   W2ref>dWref>0    -   W2>W2ref at unrestricted flow    -   W1=W2 at unrestricted flow.

The method may also include employing third, optional fourth andoptional further heating devices, in the same manner described above forW2, thereby to generate third, optional fourth and optional furtherheated spots with variable power delivery W3, W4, . . . Wn that aremaintained substantially constant over time, at unrestricted flow. Thesemay be provided along the circumference of the conduit, in the samecross-sectional plane as the heating devices providing W1 and W2, atselected points between the heating devices providing W1 and W2 and,thus, angularly spaced relative to the heating devices providing W1 andW2.

The method may then include locally measuring third, optional fourth andoptional further temperatures T4, T5 . . . Tn of the third, optionalfourth and optional further heated spots, and calculating third,optional fourth and optional further temperature differences T4 minus T3(dT3), T5 minus T3 (dT4 . . . Tn minus T3 (dTn).

The method may then further include comparing dT3, dT4 . . . dTn toreference values for dT3, dT4 . . . dTn, being dT3ref, dT4ref . . .dTnref, or comparing T4, T5 . . . Tn to a desired value for each of T4,T5 . . . Tn.

The method may then further include causing the third heating device tochange the heating power level W3, W4 . . . Wn delivered to the conduitwall respectively if

-   -   dT3, dT4 . . . dTn respectively are not equal to dT3ref, dT4ref        . . . dTnref respectively, optionally not within an allowable        deviation of dT3ref, dT4ref . . . dTnref respectively,        sufficiently to change T4, T5 . . . Tn respectively such that        dT3, dT4 . . . dTn respectively are equal to dT3ref, dT4ref . .        . dTnref respectively, optionally within an allowable deviation        of dT3ref, dT4ref . . . dTnref respectively, or;    -   T4, T5 . . . Tn respectively are not equal to, optionally within        an allowable deviation of, the desired values thereof,        sufficiently to change T4, T5 . . . Tn respectively such that        T4, T5 . . . Tn respectively are equal to, optionally within an        allowable deviation of, their respective desired values;

The method may then include calculating respective power differencesdW3, dW4 . . . dWn between W2 and W3, W4 . . . Wn respectively, andcomparing dW3, dW4, dWn respectively to respective reference values fordW3, dW4 . . . dWn, being dW3ref, dW4ref . . . dWnref.

The method may then include deriving a conclusion of a condition ofslurry flow prevailing in the conduit based relationships between dW3,dW4 . . . dWn and dW3ref, dW4ref . . . dWnref respectively, that

-   -   if absolute values of any of dW3, dW4 . . . dWn respectively are        smaller than absolute values of dW3ref, dW4ref . . . dWnref and        an absolute value of W2 is greater than an absolute value of        W2ref, there is unrestricted flow in the conduit at the        locations of the heating devices providing W3, W4 . . . Wn        respectively, in that no flow restricting bed of solid material        has formed at the locations of the relevant heating devices        providing W3, W4 . . . Wn respectively, and    -   if absolute values of any of dW3, dW4 . . . dWn respectively are        greater than absolute values of dW3ref, dW4ref . . . dWnref and        an absolute value of W2 is greater than an absolute value of        W2ref, there is partially restricted flow in the conduit, in        that a flow restricting bed of solid material has formed at the        locations of the relevant heating devices providing W3, W4 . . .        Wn respectively.

In this context, one or more, or all, of the following may apply

-   -   W2ref>dW3ref, dW4ref . . . dWnref>0    -   dW3ref, dW4ref . . . dWnref may each be equal to dWref,    -   W3, W4 . . . Wn may each be equal to W1 and W2 at unrestricted        flow.

IN ACCORDANCE WITH A SIXTH ASPECT OF THE INVENTION is provided a slurryflow condition monitoring system for electronically deriving aconclusion of a condition of slurry flow in a non-vertical conduithaving a conduit wall and which contains a slurry to flow or flowingalong the conduit, the system including:

-   -   a first heating device that is arranged and configured to        deliver heat to the conduit wall at a first heating point on the        conduit wall, which is defined at the invert of the conduit,        thereby artificially to generate a first locally heated spot on        an interior surface of the conduit wall by delivering heat to        the conduit wall at a first variable heating power level W1 that        is substantially constant over time, and    -   a second heating device that is arranged and configured to        deliver heat to the conduit wall at a second heating point on        the conduit wall, which is defined angularly spaced from the        first heating point at an angular spacing of at least 90° and        which is not spaced from the first heating point along the        length of the conduit but which lies in the same cross-sectional        plane of the conduit as the first heating point, thereby        artificially to generate a second locally heated spot on an        interior surface of the conduit wall by delivering heat to the        conduit wall at a second variable heating power level W2 that is        substantially constant over time;    -   first and second temperature sensors that are arranged locally        and configured to measure the temperatures of the first and        second heated spots respectively, thereby to obtain a first        temperature value T1 and a second temperature value T2;    -   a third temperature sensor that is arranged and configured to        measure a third reference temperature at a reference point        spaced away from the first and second heating points, thereby to        obtain a third reference temperature value T3;    -   electronic signal generating means capable of electronically        generating signals carrying the values W1, W2, T1, T2 and T3;        and    -   one or more computing devices in communication with the        electronic signal generating means operatively configured to        receive the signals carrying the values W1, W2, T1, T2 and T3,        the one or more computing devices being programmed        electronically and configured to:        -   automatically            -   calculate a first temperature difference dT1 between T1                and T3 and compare dT1 to a reference value for dT1,                dT1ref, or            -   compare T1 to a desired value for T1, T3″, that is T3                plus a predetermined value T3′,        -   automatically cause the first heating device to change the            heating power level W1 delivered to the conduit wall at the            first heating point if            -   dT1 is not equal to dT1ref, optionally not within an                allowable deviation of dT1ref, sufficiently to change T1                such that dT1 is equal to dT1ref, optionally within an                allowable deviation of dT1ref, or            -   T1 is not equal to T3″, optionally within an allowable                deviation of T3″, sufficiently to change T1 such that T1                is equal to T3″, optionally within an allowable                deviation of T3″        -   automatically            -   calculate a second temperature difference dT2 between T2                and T3 and compare dT2 to a reference value for dT2,                dT2ref, or            -   compare T2 to a desired value for T2, T3″″, that is T3                plus a predetermined value T3′″;        -   automatically cause the second heating device to change the            heating power level W2 delivered to the conduit wall at the            second heating point if            -   dT2 is not equal to dT2ref, optionally not within an                allowable deviation of dT2ref, sufficiently to change T2                such that dT2 is equal to dT2ref, optionally within an                allowable deviation of dT2ref, or;            -   T2 is not equal to T3″ ″, optionally within an allowable                deviation of T3″ ″, sufficiently to change T1 such that                T1 is equal to T3″ ″, optionally within an allowable                deviation of T3″ ″;        -   automatically calculate a power difference dW between W1 and            W2 and compare dW to a reference value for dW, dWref;        -   automatically compare W2 to a reference value for W2, W2ref,            and        -   automatically derive a conclusion of a condition of slurry            flow prevailing in the conduit based at least on a            relationship between dW and dWref and between W2 and W2ref,            that            -   if an absolute value of dW is smaller than an absolute                value of dWref and an absolute value of W2 is greater                than an absolute value of W2ref, there is unrestricted                flow in the conduit, in that no flow restricting bed of                solid material has formed at the invert of the conduit,            -   if an absolute value of dW is greater than an absolute                value of dWref and an absolute value of W2 is greater                than an absolute value of W2ref, there is partially                restricted flow in the conduit, in that a flow                restricting bed of solid material has formed at the                invert of the conduit, and            -   if an absolute value of W2 is smaller than an absolute                value of W2ref, there is restricted flow in the conduit,                in that flow in the conduit has virtually ceased. That                W1 and W2 are substantially constant over time would                typically apply at unrestricted flow in the conduit,                since W1 and W2 would be varied when there is a change                in flow conditions in the conduit in accordance with the                method of the invention.

That W1 and W2 are substantially constant over time would typicallyapply at unrestricted flow in the conduit, since W1 and W2 would bevaried when there is a change in flow conditions in the conduit inaccordance with the method of the invention.

One or more, or all, of the following conditions may typically apply toW2ref, dWref, W1 at unrestricted flow, and W2 at unrestricted flow:

-   -   W2ref>0    -   W2ref>dWref>0    -   W2>W2ref at unrestricted flow    -   W1=W2 at unrestricted flow.

The configuration of the system may also include employing third,optional fourth and optional further heating devices, in the same mannerdescribed above for either W1 or W2, thereby to generate third, optionalfourth and optional further heated spots with variable power deliveryW3, W4, . . . Wn that are maintained substantially constant over time,at unrestricted flow. These may be provided along the circumference ofthe conduit, in the same cross-sectional plane as the heating devicesproviding W1 and W2, at selected points between the heating devicesproviding W1 and W2 and, thus, angularly spaced relative to the heatingdevices providing W1 and W2.

The configuration of the system and the programming and configuration ofthe computing device may then include locally measuring fourth, optionalfifth and optional further temperatures T4, T5 . . . Tn of the third,optional fourth and optional further heated spots, and calculatingthird, optional fourth and optional further temperature differences T4minus T3 (dT3), T5 minus T3 (dT4 . . . Tn minus T3 (dTn).

The programming and configuration of the computing device may thenfurther include comparing dT3, dT4 . . . dTn to reference values fordT3, dT4 . . . dTn, being dT3ref, dT4ref . . . dTnref, or comparing T4,T5 . . . Tn to a desired value for each of T4, T5 . . . Tn.

The programming and configuration of the computing device may thenfurther include causing the second heating device to change the heatingpower level W3, W4 . . . Wn delivered to the conduit wall respectivelyif

-   -   dT3, dT4 . . . dTn respectively are not equal to dT3ref, dT4ref        . . . dTnref respectively, optionally not within an allowable        deviation of dT3ref, dT4ref . . . dTnref respectively,        sufficiently to change T4, T5 . . . Tn respectively such that        dT3, dT4 . . . dTn respectively are equal to dT3ref, dT4ref . .        . dTnref respectively, optionally within an allowable deviation        of dT3ref, dT4ref . . . dTnref respectively, or;    -   T4, T5 . . . Tn respectively are not equal to, optionally within        an allowable deviation of, the desired values thereof,        sufficiently to change T4, T5 . . . Tn respectively such that        T4, T5 . . . Tn respectively are equal to, optionally within an        allowable deviation of, their respective desired values.

The programming and configuration of the computing device may theninclude calculating respective power differences dW3, dW4 . . . dWnbetween W2 and W3, W4 . . . Wn respectively, and comparing dW3, dW4, dWnrespectively to respective reference values for dW3, dW4 . . . dWn,being dW3ref, dW4ref . . . dWnref.

The programming and configuration of the computing device may theninclude deriving a conclusion of a condition of slurry flow prevailingin the conduit based relationships between dW3, dW4 . . . dWn anddW3ref, dW4ref . . . dWnref respectively, that

-   -   if absolute values of any of dW3, dW4 . . . dWn respectively are        smaller than absolute values of dW3ref, dW4ref . . . dWnref and        an absolute value of W2 is greater than an absolute value of        W2ref, there is unrestricted flow in the conduit at the        locations of the heating devices providing W3, W4 . . . Wn        respectively, in that no flow restricting bed of solid material        has formed at the locations of the relevant heating devices        providing W3, W4 . . . Wn respectively, and    -   if absolute values of any of dW3, dW4 . . . dWn respectively are        greater than absolute values of dW3ref, dW4ref . . . dWnref and        an absolute value of W2 is greater than an absolute value of        W2ref, there is partially restricted flow in the conduit, in        that a flow restricting bed of solid material has formed at the        locations of the relevant heating devices providing W3, W4 . . .        Wn respectively.

In this context, one or more, or all, of the following may apply

-   -   W2ref>dW3ref, dW4ref . . . dWnref>0    -   dW3ref, dW4ref . . . dWnref may each be equal to dWref,    -   W3, W4 . . . Wn may each be equal to W1 and W2 at unrestricted        flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of illustrative example only,with reference to the accompanying diagrammatic drawings in which

FIG. 1 shows, in cross sectional view, a system in accordance with thesecond aspect of the invention in conjunction with a conduit in the formof a pipe;

FIG. 2 shows a block diagram of operations performed according to themethod of the first aspect of the invention by/under direction of thecomputing means/device of the system of the second aspect of theinvention; and

FIG. 3 shows a screenshot of electronically generated signals obtainedand used in the system of the second aspect of the invention inimplementing the method of the first aspect of the invention, to deriveconclusions and provide visible indications of slurry flow conditionsprevailing in a conduit.

FIG. 4 shows a plot of temperatures, temperature differentials, andpower levels of the system of the sixth aspect of the invention whenperforming the method of the fifth aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, and particularly to FIG. 1, reference numeral10 generally indicates a slurry flow condition monitoring system inaccordance with the second aspect of the invention.

The system 10 includes a conduit in the form of a pipe 12. The pipe 12has a conduit wall which is a pipe wall 14, having a thickness ofbetween about 2 and about 20 mm, both values inclusive. The pipe 12 iscircular cylindrical.

A first heating device 16 is mounted on an exterior surface of the pipewall 14 at the invert of the pipe. The first heating device 16 has aheated working surface that is in contact with the exterior surface ofthe pipe wall 14 at a first heating point 17 along the exterior surfaceof the pipe wall 14, and delivers heat to the pipe wall 14 at the firstheating point 17. It will be appreciated that the first heating point 17is at the invert of the pipe 12. The first heating device 16 deliversheat to the pipe wall 14 at a first heating power level that ismaintained substantially constant over time. The delivery of heat to theexterior surface of the pipe wall 14 by the first heating device 16 atthe first heating point 17 results in a first locally heated spot 18being artificially generated on an interior surface of the pipe wall 14due to conductive heat transfer through the pipe wall 14.

A second heating device 20 is also mounted on the exterior surface ofthe pipe wall 14. The second heating device 20 also has a heated workingsurface that is in contact with the exterior surface of the pipe wall 14at a second heating point 21 along the exterior surface of the pipe wall14, and delivers heat to the pipe wall 14 at the second heating point21. The second heating device delivers heat to the pipe wall 14 at asecond heating power level that is equal to the first heating powerlevel and is also maintained substantially constant over time. As in thecase of the first heating device 16, the delivery of heat to theexterior surface of the pipe wall 14 by the second heating device 20artificially generates a second locally heated spot 22 on the interiorsurface of the pipe wall 14 due to conductive heat transfer through thepipe wall 14.

The first and second heating points 17, 21 are angularly spaced fromeach other about a central longitudinally extending axis ‘A’ of the pipe12. Relative mounting of the first heating device 16 and the secondheating device 20 about the axis A is therefore also such that the firstand second heated spots 18, 22 are generated at locations that areequally angularly spaced from each other about the axis ‘A’. The angularspacing is, in accordance with the invention, at least 90°. It is,however, preferred that the angular spacing is greater than 90°. Mostpreferably, and as illustrated in FIG. 1, the angular spacing is 120°.

The system 10 also includes first and second temperature sensors 16A,20A that are arranged locally to measure the temperature of each of thefirst and second heated spots 18, 22 respectively, thereby to obtainfirst and second temperature values T1, T2. This measurement isindependent of the first and second heating devices 16, 20. Since thefirst and second temperature sensors 16A, 20A operate in close proximityto the heating devices 16, 20, however, the first and second temperaturesensors 16A, 20A are illustrated as being included in the heatingdevices 16, 20. This is merely to simplify the drawing and would notnecessarily hold true in practice.

The temperatures of the first and second heated spots 18, 22 aremeasured at the respective heating points 17, 21 in substantially thesame plane, or in a plane slightly upstream of the plane in which theheating points 17, 21 and heating spots 18, 22 are located, e.g. 15 mmupstream therefrom. The temperature measurement is preferably continuousor at predetermined intervals over time.

In a particular embodiment of the invention, all of the heating devicesand their associated temperature sensors are mounted a distance of 15 mmfrom each other (centre to centre) on an aluminium base plate. This baseplate is then water-tightly screwed to a head, which also provides acable gland. Cable ends are soldered onto contact points on the baseplate. 3 cores are needed to control of heat created by the transistor,and two cores for the sensor, which is desirably a Pt100 sensor. Theheads should be mounted such that their cable glands point downstream ofthe flow in the pipe 12, so that the Pt100 is 15 mm upstream of theheating device. Then the heating devices are on exactly the same crosssectional plane, whereas all three temperature sensors are in their ownplane, which is however still functionally speaking in the same plane asthe heating devices, also depending on how thick the plane is defined tobe. The base plate is typically 3 mm thick.

The system 10 further includes a reference temperature sensor 24. Whilethe inclusion of this reference temperature sensor 24 is optional inaccordance with the invention, it is preferred that it is included. Thereference temperature sensor 24 is provided at a reference point 25,which is a point along the pipe wall 14, and measures a referencetemperature to obtain a reference temperature value T3. The referencetemperature is therefore a temperature of the pipe wall 14. Noartificial heating is supplied at the reference point. Preferably, thereference sensor is also a Pt100 sensor.

The reference point 25 is angularly spaced as far as possible from eachof the first and second heating points 17, 21. When defined on the pipewall 14, as is presently the case, the reference point is thereforeequidistally spaced along the pipe wall 14 from both of the first andsecond heated spots 18, 22. Angular spacings between the reference point25 and each of the first and second heating points 17, 21 are thereforealso equal, being 120° in the illustrated embodiment. It will beappreciated that, in the illustrated embodiment, the first and secondheating points 17, 21 and the reference point 25 are thereforeequiangularly spaced from each other about the axis A.

The first and second heating points 17, 21 and the reference point 25all lie in the same cross-sectional plane of the conduit. The first andsecond heated spots 18, 22 therefore also lie in this plane.

The system 10 also includes an electronically programmable computingdevice 26. The first and second temperature sensors 16A, 20A and thereference temperature sensor 24 are in communication with the computingdevice 26 along respective electronic communication lines 28, 30 and 32.The first and second temperature sensors 16A, 20A and the referencesensor 25 are also operatively associated with one or more electronicsignal generating means (not illustrated) which are capable ofelectronically generating signals carrying the values of T1, T2 and T3,which are to be communicated to the computing device 26 along thecommunication lines 28, 30 and 32 respectively. By “operativelyassociated” is meant that the electronic signal generating means canreceive the measured values T1, T2 and T3 in order electronically togenerate the signals carrying these values.

The computing device 26 is configured and programmed operatively toreceive the electronically generated signals and derive a conclusion ofthe condition of slurry flow conditions prevailing in the pipe 12 from afirst temperature difference, which is T1 minus T2, and a secondtemperature difference, which is T2 minus T3. The computing device isalso programmed to calculate these temperature differences from thetemperature values communicated to it in the respective signals. By“operatively receive” is meant that the computing device 26 receives thesignals carrying the values T1, T2 and T3, and interprets or decodes thesignals in whichever manner necessary in order to calculate theabovementioned temperature differences. With respect to the signals, itwill be appreciated that embodiments can exist in which a singlecombined signal carrying all of the values of T1, T2 and T3 iscommunicated, rather than respective signals for each value.

The computing device 26 includes or is in controlling communication withvisual and/or audio indicating means, or indicators, which providevisible and/or audible indications of selected conditions of slurry flowin the pipe 14, when concluded by the computing device. These are notillustrated. The indicators are configured to provide respective visibleand/or audible indications on the basis of an output conclusion derivedby the computing means, indicating that the output conclusion has beenderived, which output conclusion is one of at least

-   -   (i) that a settled particle bed has formed at the invert of the        conduit, i.e. at the first heated spot; and    -   (ii) that there is no flow in the conduit.

The computing device 26 is programmed electronically to automaticallyderive a conclusion that a settled particle bed has formed at the invertof the conduit on the basis of the relationship between the firsttemperature difference and a first reference parameter, which is areference parameter for the first temperature difference. Moreparticularly, the first reference parameter is a desired value of thefirst temperature difference and has a value of 0 (zero). A conclusionthat a settled particle bed has formed at the invert of the conduit isderived by the computing device 26 on the basis that the firsttemperature difference is greater than 0.

The computing device 26 is programmed electronically to automaticallyderive a conclusion of no flow in the conduit on the basis of therelationship between the second temperature difference and a secondreference parameter, which is a reference parameter for the secondtemperature difference or for T2. More particularly, the secondreference parameter is a predetermined undesired change in the secondtemperature difference over a predetermined time period or a thresholdvalue for the second temperature difference, or a threshold value forT2. Only the first option is further discussed, but it may equally bethe second or third options, as described in accordance with theinvention.

Specifically, the predetermined undesired change in the secondtemperature difference is 0.25° C. and the predetermined time period is10 seconds. A conclusion that there is no flow in the conduit istherefore derived on the basis that the second temperature differencehas increased with 0.25° C. or more within a time period of 10 seconds.The computing device 26 is therefore programmed electronically toautomatically note changes in the second temperature difference, and toautomatically conclude that the condition of slurry flow in the pipe 12is that there is no flow, on the basis that a change in the secondtemperature difference over the predetermined time period is equal to,or exceeds the predetermined undesired change over the predeterminedtime period.

The computing device 26 is programmed such that a conclusion derived onthe basis of the second temperature difference that there is no flow inthe pipe 12 automatically overrides any other conclusion derived on thebasis of the first or any other temperature differences. The conclusionthat there is no flow in the pipe 12 is therefore always the outputconclusion when it is derived by the computing device 26. In all othercircumstances, the conclusion/s derived on the basis of the first and/orany other temperature differences that a settled bed has formed in theconduit is the output conclusion, or provides a group of outputconclusions. The computing device 26 is also programmed electronicallyto automatically note, as a threshold value, the value of T2 minus T3when a conclusion that there is no flow in the conduit has been derived,and such that the conclusion that there is no flow in the conduitcontinues to override any conclusion derived on the basis of the firstor any other temperature differences until the value of T2 minus T3 isagain below the threshold value of T2 minus T3.

The system 10 further includes, between the first heating point 17 andthe second heating point 21, at angular spacings of less than 90° fromthe first heating point, third and fourth heating device/temperaturesensor combinations 34/34A, 36/36A operable to generate, by deliveringheat to third and fourth heating points (not illustrated) along theexterior surface of the pipe wall 14, third and fourth locally heatedspots (also not indicated on the drawing) on the interior surface of thepipe wall 14. This is achieved in the same manner in which generation ofthe first and second heated spots 18, 22 is achieved. Heating powerlevels of the third and fourth heating devices 34, 36 are the same asthe heating power levels of the first and second heating devices 12, 20.

The third and fourth heating device/temperature sensor combinations34/34A, 36/36A operate in the same manner as the first and secondheating device/temperature sensor combinations 16/16A, 18/18A to obtaintemperature values, calculate temperature differences and deriveconclusions of the conditions of slurry flow at the third and fourthheated spots. More specifically, fourth and fifth temperature values T4,T5 of the third and fourth heated spots are measured and communicated tothe computing device 26. The computing device 26 then calculates thirdand fourth temperature differences T4 minus T2 and T5 minus T2. On thebasis of the relationship between the third and fourth temperaturedifferences and respective third and fourth reference parameterstherefor, respective conclusions are derived by the computing device 26of the condition of slurry flow prevailing at the third and fourthheated spots. The third and fourth reference parameters are desiredvalues of the third and fourth temperature differences, each being zero.The computing device 26 is programmed to derive a conclusion that asettled particle bed has formed at the third and fourth heated spots,respectively on the basis that the third and fourth temperaturedifferences are greater than 0. It will be appreciated that the use ofsuch third and fourth heating device/temperature sensor combinations34/34A, 36/36A and the information obtained therefrom, allows thecomputing device 26 to derive a conclusion of the profile of a settledparticle bed, since the development of the settled particle bed can thenbe monitored as the third and fourth temperature differences are notedas becoming greater than 0. While the second temperature difference isnot the output conclusion, the first, third, fourth and furthertemperature differences, when individually greater than zero, maytherefore be a group of output conclusions. In this manner, not only isa conclusion of the formation of a bed derived, but also a conclusion ofprofile characteristics of the bed.

DISCUSSION

While there is unrestricted and free flow of slurry in the pipe 12, heatis removed from the first and second heated spots 18, 22 due toconvective heat transfer. Since the rate of heat removal from the firstand second heated spots 18, 22 will be more or less equal in such acase, the difference between the first and second temperature values (T1minus T2, i.e. the first temperature difference) would, when the sameconstant level of heating power is delivered by each of the heatingdevices 16, 20 with the temperatures of the first and second heatedspots 18, 22 also being equal, approximate zero. A zero differentialbetween the first and second temperature values T1, T2 (i.e. a zerovalue of the first temperature difference) should, and does depending onthe circumstances, therefore cause a conclusion of unrestricted and freeflow conditions in the conduit being derived. While this holds true whena settled bed forms while there is still flow in the conduit, it doesnot necessarily remain true if flow conditions deteriorate andeventually result in a condition of no flow.

When flow conditions in the pipe 12 deteriorate starting from acondition of full flow, for example as a result of loss of pumping powerthat drives flow in the conduit and/or as a result of a change in slurryproperties, thereby causing the formation of a settled particle bed atthe invert of the pipe 12, flow at the invert becomes restricted.Initially, such a settled particle bed may still be in motion, being inthe form of a sliding bed. Later, the bed may become completelystationary if solid particles continue to settle from suspension in theevent that flow conditions do not improve.

While the bed is relatively shallow, flow above the bed may continue. Insuch a case the rate of heat removal from the first heated spot 18 wouldbe perceivably less than the rate of heat removal from the second heatedspot 22, due to the difference in flow conditions. Consequently, adifference between the first and second temperature values T1, T2 wouldbe observed, with the result that the first temperature difference is nolonger zero. Observing such a difference therefore requires a conclusionto be derived that a settled particle bed has formed at the invert ofthe pipe 12.

If flow conditions still do not improve when a bed of sediment hasformed at the invert of the pipe 12, the bed may continue to grow. Thiswould necessarily impact on flow above the bed, which would becomeprogressively more restricted, flowing slower and slower, potentiallyeventually coming to a complete standstill. As flow above the bed slows,the rate of heat removal at the second heated spot 22 also slows. Itwill be appreciated that this will cause the second temperature value T2progressively to increase until, when there is no flow in the pipe, itis again equal to the first temperature value T1. This increase in thesecond temperature value T2 necessarily affects the value of the firsttemperature difference (between the first and second temperaturevalues), eventually erasing it when the first and second temperaturevalues are again equal. In such a case, the abovementioned conclusion offree and unrestricted slurry flow when there is no difference betweenthe first and second temperature values would not hold true and wouldtherefore be misleading to an operator, who might assume, incorrectly,that flow has recommenced. It is in this scenario in which the secondtemperature difference comes into play, since slowing of the flow rateabove the settled bed and consequent slowing of heat removal from thesecond heated spot 22 also causes the value of the second temperaturedifference to change. When the magnitude of this change is such that itis equal to or exceeds the second reference parameter as hereinbeforedefined, an overriding conclusion of no flow is drawn despite the factthat the value of the first temperature difference is again movingtoward or approximating zero.

Referring to FIG. 2, the abovementioned functionality is illustrated byway of a block diagram. The values T1, T2, T3 and T4 (as represented incolumn 1 of FIG. 2) are communicated to the computing device 26 by meansof the electronically generated signals. The computing device 26 thencalculates the first, second and third temperature differences(respectively ΔT1, ΔT2, and ΔT3). For each temperature difference, areference parameter is programmed into the computing device 26(respectively being designated as ΔT1ref, ΔT2ref, and ΔT3ref). As willbe appreciated from the foregoing discussion, ΔT1ref and ΔT3ref arediscrete values of zero, while ΔT2ref is defined and set to be theactual ΔT2 value at that very point in time, when a predeterminedundesired change in the value of ΔT2 over a predetermined time periodoccurred. ΔT2ref is therefore set only when the predetermined undesiredchange in the value of ΔT2 occurs. Before it occurs, ΔT2 is naturallybelow what ΔT2ref would be when it is set.

The computing device 26 is also programmed to determine the relationshipbetween ΔT1, ΔT2, and ΔT3 and ΔT1ref, ΔT2ref, and ΔT3ref respectively.As is represented in column 3 of FIG. 2, the computing device 26 derivescertain conclusions of the conditions of slurry flow in the pipe 12,based on the relationship of the ΔT1, ΔT2, and ΔT3 and ΔT1ref, ΔT2ref,and ΔT3ref respectively, as set out in column 2 of FIG. 2. Theserelationships and the conclusions that they necessitate speak forthemselves from the drawing, and no further detail is provided. Based onthe conclusions, each of which is an output conclusion for therelationship grouping in column 2 that requires it, visible and/oraudible outputs are provided by the visual and/or audio indicating meansincluded in the system 10. These indicating means may, in oneembodiment, include green, orange and red lights. The computing deviceis programmed such that a conclusion of “full flow, no bed” wouldprovide an illuminated green light, that conclusions of “constrainedflow, bed at T1, no bed at T3” and “constrained flow, bed at T1, bed atT3” would provide an illuminated yellow light, and that a conclusion of“no flow” would provide an illuminated red light. The latter conclusionoverrides all other conclusions. Note that in column 3 of FIG. 2, T1 andT4 are used to represent the respective heated spots for whichconclusions of the condition of slurry flow are being derived by thecomputing means.

Against the background provided above, deriving an indication of slurryflow conditions in accordance with the method of the invention is on thebasis of the first temperature difference while any changes in thesecond temperature difference are below the second reference parameter.When a change in the second temperature difference exceeds thepredetermined reference parameter, deriving a conclusion of slurry flowconditions in accordance with the method of the invention is based onthe relationship between the second temperature difference and thesecond reference parameter.

Results of an experimental test of the efficacy of a system as taughtherein, implementing a method taught herein, except the use of T4.

Seven signals and 2 thresholds are shown in FIG. 3, which was createdduring a test of the overall logic of the method of the invention andits computing algorithms.

The ambient temperature and the reference temperature T3, which weremeasured, gradually increased during the test run. The values of theseare not shown to minimize the clutter in the chart. It will beappreciated that the computing algorithms of the method of the inventionuse temperature differences, which in any event eliminate ambienttemperature effects. Thus, T1 and T2 essentially float on the changingT3 reference temperature.

The test results show the performance of the system and the method ofthe invention in response to a ramping down of the flow rate to zerofrom a condition of full flow of slurry in the pipeline. After about 10minutes at zero flow rate, the flow rate was again ramped up. Thus, thetest represents a complete cycle from full flow to no flow and back tofull flow.

An online output signal (PLC controlled) provides distinct voltagelevels to communicate the computed flow conditions to either an operatorby means of acoustic and/or visual alarms, or to a PLC for predefinedresponses in according to options available at specific operations.

Key steps shown in FIG. 3 are as follows:

1) initial auto-calibration, including switching on the heating powerduring full flow2) automatically setting a threshold (first reference parameter) for(T1-T2) at 0.4 Deg C. above (T1-T2)3) computing signals to trigger a “settled bed” indication4) computing signals to trigger a “no flow” indication5) computing signals to remove the “no flow” condition6) computing signals to remove the “settled bed” condition after allsettled particles have been re-suspended into full flow.

Table 1 below provides a description of the signals and the relevantaxes to which they refer. The units of the thresholds are also deltatemperatures in Deg C. Thus they are also shown in the Delta Tempsscale.

TABLE 1 Signals and axes Signal Marker Axis Label Flow rate in m³/h withdashed line for zero none Flow m³/h Heating power none Heat % T1 −temperature at invert ◯ Real Temps T2 − temperature at top Δ Real TempsT2 − T3 ⋄ Delta Temps T1 − T2 □ Delta Temps Threshold top (TH_(top))dashed line and ⋄ Delta Temps Threshold invert (TH_(inv)) dashed lineand □ Delta Temps Computed online output in Volts for none PLC CTRLindicators

Table 2 that follows explains the initiated processes and the computedconditions.

TABLE 2 Initiated processes and computed conditions LED Output statusand Direct Derived Signal transition of Time Action/process ConsequenceConclusion (PLC Ctrl) indicators 13:31:00 Full flow at 65 m³/h Nosettled Full flow Baseline at Green is particles at the 1.6 V ON invertof the pipe 13:31:35 In response to an Both real Full flow Baseline atGreen is external calibration temperatures T1 1.6 V ON command: Heatingand T2 increase power changes from zero to 100% for both sensors13:33:00 (T1 − T2) and A threshold of Full flow Baseline at Green is (T2− T3) 0.4 Deg C. above 1.6 V ON are stabilized the stabilised (T1 − T2)is noted for future use. 13:33:30 Ramping down of Full flow Baseline atGreen is flow rate commences 1.6 V ON 13:34:45 At 46 m³/h, particlesSudden increase Settled bed Increase to Yellow settle and become in T1 −T2. 2.4 V goes ON stationary, thus Threshold for Green reducing the heatinvert is now goes OFF removal from T1 transgressed by T1 − T2 movingupwards. 13:37:10 As flow approaches T1 − T2 starts to Settled bedIncrease to zero, T2 heats up drop back 2.4 V towards its threshold13:37:30 The ‘rate of rise’ of At this point in No flow Increase to Redgoes T2 − T3 exceeds a time, the T2 − T3 3.2 V ON preset value (e.g.0.25 value is noted Yellow Deg C. in 10 seconds) (i.e. 3.7 Deg C.) goesOFF and stored as a reference parameter (TH_(top)). Threshold for T2 −T3 is transgressed upwards 13:40:40 T1 − T2 drops below its No effect,No flow Increase to NB: When reference parameter as T2 − T3 3.2 V T1 −T2 is (TH_(invert)) is higher below TH_(invert), than TH_(top). thiswould indicate “false green”, but is overridden by red LED 13:46:00 Pumpstarts and some Minor cooling No flow Increase to NB: When minormovement of of T2 reduces 3.2 V T1 − T2 is supernatant water T2 − T3,and thus below TH_(invert), occurs, but the flow is increases T1 − T2.this would indicate still too small to be “false green”, recognized bythe but is flow meter. overridden by red LED 13:47:50 Meaningful flow T2− T3 is No flow Increase to NB: When commences and flow dropping 3.2 VT1 − T2 is meter starts to provide towards its below TH_(invert), anoutput. T2 is now threshold. The this would indicate being rapidlycooled thermal inertia “false green”, by the flow of delays the but issupernatant water. passing of the overridden Solids are being TH_(top)by about 1 by red LED gradually picked from minute. the top of thesettled bed. 13:48:50 Further cooling down T2 − T3 passes its Settledbed Decrease Red goes of T2. reference to 2.4 V OFF T1 − T3 is reachinga parameter TH_(top) Yellow saturation level even of 3.7 Deg C. goes ONwhile the bed is eroded from the top due to increasing flow rate.13:50:20 Rapid decrease in T1 T1 − T2 decreases due to slurry flow atrapidly. Again, the invert, after all some thermal settled solids wereinertia delays removed. the transgressing of the TH_(inv) downwards byone minute. 13:51:15 Further cooling of T1 T1 − T2 passes Full flowDecrease Yellow after solids are all re- TH_(inv) to 1.6 V goes OFFsuspended into the downwards. Green slurry goes ON

The applicant believes that the invention as described provides anelegant and effective approach to monitoring and determining theundesired occurrence as well as the vertical extent of sedimentation atthe pipe invert in a pipeline. The invention is in this regard notlimited to pipelines, but could also find application in open conduitswhich are not visually monitored.

Exemplary embodiment of a system taught herein, implementing a methodtaught herein.

Referring again to FIG. 1, in an alternative embodiment of the system10, the first and second heating devices 16, 20 are variable powerheating devices, each delivering heat to the pipe wall 14 respectivelyat the first and second heating points 17, 21 respectively at a firstheating power level W1 and at a second heating power level W2, each ofwhich is maintained substantially constant over time, except whenadjusted as described below.

In the alternative embodiment of the system 10, the sensors 16A, 20A maybe incorporated in their associated heating devices 16, 20, e.g. beingin the form of heated sensor heads.

Further, in the alternative embodiment of the system 10, the electronicprogramming and configuration of the computing device 26 is different tothat hereinbefore described. More specifically, the computing device 26is electronically programmed and configured to

-   -   automatically        -   calculate a first temperature difference dT1 between T1 and            T3 and compare dT1 to a reference value for dT1, dT1ref, or        -   compare T1 to a desired value for T1, T3″, that is T3 plus a            predetermined value T3′,    -   automatically cause the first heating device to change the        heating power level W1 delivered to the conduit wall at the        first heating point if        -   dT1 is not equal to dT1ref, optionally not within an            allowable deviation of dT1ref, sufficiently to change T1            such that dT1 is equal to dT1ref, optionally within an            allowable deviation of dT1ref, or        -   T1 is not equal to T3″, optionally within an allowable            deviation of T3″, sufficiently to change T1 such that T1 is            equal to T3″, optionally within an allowable deviation of            T3″    -   automatically        -   calculate a second temperature difference dT2 between T2 and            T3 and compare dT2 to a reference value for dT2, dT2ref, or        -   compare T2 to a desired value for T2, T3″″, that is T3 plus            a predetermined value T3′″;    -   automatically cause the second heating device to change the        heating power level W2 delivered to the conduit wall at the        second heating point if        -   dT2 is not equal to dT2ref, optionally not within an            allowable deviation of dT2ref, sufficiently to change T2            such that dT2 is equal to dT2ref, optionally within an            allowable deviation of dT2ref, or;        -   T2 is not equal to T3″″, optionally within an allowable            deviation of T3″″, sufficiently to change T1 such that T1 is            equal to T3″″, optionally within an allowable deviation of            T3″″;    -   automatically calculate a power difference dW between W1 and W2        and compare dW to a reference value for dW, dWref;    -   automatically compare W2 to a reference value for W2, W2ref, and    -   automatically derive a conclusion of a condition of slurry flow        prevailing in the conduit based at least on a relationship        between dW and dWref and between W2 and W2ref.

In deriving a conclusion of the condition of slurry flow prevailing inthe conduit,

-   -   if an absolute value of dW is smaller than an absolute value of        dWref and an absolute value of W2 is greater than an absolute        value of W2ref, the computing device concludes that there is        unrestricted flow in the conduit, in that no flow restricting        bed of solid material has formed at the invert of the conduit,    -   if an absolute value of dW is greater than an absolute value of        dWref and an absolute value of W2 is greater than an absolute        value of W2ref, the computing device concludes that here is        partially restricted flow in the conduit, in that a flow        restricting bed of solid material has formed at the invert of        the conduit, and    -   if an absolute value of W2 is smaller than an absolute value of        W2ref, the computing device concludes that there is restricted        flow in the conduit, in that flow in the conduit has virtually        ceased.

Thus, the computing device 26 is in controlling communication with thefirst and second heating devices 16, 20 respectively, to control thefirst and second heating devices 16, 20 respectively by selectivelycausing the first and second heating devices 16, 20 respectively tochange the first and second heating power levels W1, W2 respectively, inthe circumstances discussed above.

Example 1 of a System of the Sixth Aspect of the Invention in Operation

The following parameters are provided:

-   -   W1 (supplied by first heating device 16)    -   T1 (supplied by W1 and measured by temperature sensor 16A)    -   W2 (supplied by second heating device 20)    -   T2 (supplied by W2 and measured by temperature sensor 20A)    -   W2ref (predetermined constant reference value for W2)    -   dW=W2−W1    -   dWref (predetermined constant reference value for dW)    -   T3=measured by temperature sensor 24    -   (T3 is a floating reference value for T1 and T2 respectively)    -   dT1=T1-T3    -   dT2=T2-T3

For the example

-   -   W2ref=8    -   W1 at unrestricted flow is 10    -   W2 at unrestricted flow is 10    -   dWref=2    -   T3=24    -   T1 and T2=32 at full flow    -   It is desired for dT1 and dT2, respectively, to approximate a        desired constant, which is 8° C. in the example, alternatively        meaning that predetermined values T3′ and T3′″ are equal to 8,        with T3″ and T3″″ respectively being T3+8.

At full flow

-   -   dW=W2−W1=10−10=0<2 (dWref)    -   W2=10>8 (W2ref)    -   dT1=8° C.    -   dT2=8° C.    -   Thus, dW<dWref and W2>W2ref which are the conditions for a        conclusion of full flow

A bed forms at the invert, with flow above the bed

-   -   T1 increases    -   dT1 increases

Controller for W1 responds

-   -   decreases power to W1 to 4    -   dT1 restored    -   dW=W2−W1=10−4=6>2 (dWref)    -   W2=10>8 (W2ref)    -   Thus, dW>dWref and W2>W2ref which are the conditions for a        conclusion of bed formation, i.e. partially restricted flow.

Flow deteriorates and ultimately gets fully restricted

-   -   T1 increases    -   T2 increases    -   dT1 increases    -   dT2 increases

Controllers for W1 and W2 respond

-   -   further decreases power to W1 to 2    -   decreases power to W2 to 5<8 (W2ref)    -   dT1 restored    -   dT2 restored    -   dW=W2-W1=5−2=3>2 (dWref)    -   Thus, dW>dWref, but since W2<W2ref, a conclusion of no flow is        drawn (it may be that under no flow dW<dWref, but the overriding        factor (rule) is W2<W2ref)

Example 2 of a System of the Sixth Aspect of the Invention in Operation

Referring now to FIG. 4, which illustrates a chart of the performance ofthe system of the sixth aspect of the invention using individualPID-controllers for two heated sensor heads 16, 20. The followingparameters, separated into four separate groups, are shown in the chart:

Changing the Process Condition:

-   -   Flow Rate, which was set to zero flow (restricted flow) at the        start, then to a flow rate with a bed (partially restricted        flow), and then to a high flow rate with no bed (unrestricted        flow). Thus, the three flow rates create the three distinct        process conditions to be identified by the instrumentation.

Sensing the Temperature Responses to Variable Flow and/or BedConditions:

-   -   T1Bot is T1, provided and measured by the heated bottom heating        device/sensor 16, 16A at pipe invert, automatically controlled        to be about 8° C. above the reference temperature.    -   T2Top is T2, provided ad measured by the heated top heating        device/sensor 20, 20A, automatically controlled to be also about        8° C. above the reference temperature.    -   T3Ref is T3, measured by the unheated reference sensor 24 to        provide a set point, based on slurry temperature.

Controlling to Maintain the Set Points:

-   -   W1Bot is W1, the variable heat supplied to the bottom sensor 16A        to maintain the desired set point under all process conditions.        For this test, the set point for both heating devices 16, 20, as        mentioned above, is 8° C. above T3 (i.e. the desired values for        dT1 and dT2 are 8, alternatively that T3′ and T3′″ are each 8,        and T3″ and T3″ ″ are each T3+8). It varies naturally, as the        slurry temperature changes, e.g. from the energy supplied by the        centrifugal pump in the recirculating pipe loop.    -   W2Top is W2, the variable heat supplied to the top sensor 20A to        maintain the desired set point under all process conditions.

Computing to Derive at a Conclusion and its Visualisation:

-   -   dW is the difference between the heat supplied to the two        sensors.    -   TH NeF is W2ref, the threshold for ‘Not enough Flow’, which is        set to trigger the condition of ‘no flow’ (restricted flow), as        well as the condition of re-commencing the flow, by using W2        Top.    -   TH Bed is dWref, the threshold for a settled bed (partially        restricted flow) at the bottom of the pipeline, and in turn for        bed erosion.    -   Visualisation of computed conditions: This has been done in        practice with a set of 3 different LEDs (red, yellow and green).        The ON condition of the relevant LED is shown at the bottom of        the chart. E.g. the solid red line represents the period of ‘Not        enough Flow’, i.e ‘No Flow’. The yellow line represents the        settled ‘Bed’ condition (with flow). The green line represents        flow with ‘No Bed’. The LEDs are triggered by the various        algorithms/rules, as well as applicable over-riding rules, as        mentioned in the original specifications.

TABLE 3 Example 2 of the system of the sixth aspect of the invention,with reference to FIG. 4 Comments/Flow Rate Time Sensing/ConditionResponses/Explanations Changes 4 Stable temperatures The settled bed‘acts’ like an Pipe loop has been standing and stable, but unequalinsulator and thus less heat is for a while with a settled bed. heat issupplied to both needed to maintain the set point for sensors. thebottom sensor, when compared to the top sensor. Top sensor ‘sees’ clearwater, which takes more heat away than the settled bed, even during noflow conditions. 5 T2Top drops more than Controller detects the drop ofOnly a low flow rate is T1Bot due to cold T2Top and thus increasesgradually initiated to avoid erosion of water flowing past the the heatto the top sensor. the bed. sensor, thereby cooling the hot spot. 6W2Top increases and The red LED for ‘Not enough Flow’ This output is thekey insight 7 passes upwards through turns OFF, and the yellow LED whichthe patented 8 the threshold for ‘Not goes ON to indicate a bedcondition, technology provides to the enough Flow’, TH with some flowabove. operator/pump control. NeF. 14 The temperature T1Bot Thecontroller detects the Flow rate is increased to 15 drops rapidly due tothe temperature drop and reacts by significantly above the 16 erosion ofthe increasing the heat W1Bot. Thus deposition velocity, thus theinsulating bed, while T1Bot increases until it reaches the bed iscompletely eroded. the heat supply is still set point again, being 8° C.above the low. slurry temperature, T3Ref. 17 dW drops below Systemcalculates that both criteria The system response could threshold for NoBed. are met to qualify for a green LED be improved to be faster thanfor flow with no bed: 3 Minutes, but that could W2 > TH NeF, as well asdW < TH Bed. result in an undesired under- swing of dW when a beddevelops, i.e. at 55 Minutes in upper chart. 22-37 Stable and equal heatdW is zero and clearly below the This is regarded as the supply to bothsensors, threshold for no bed. normal operation without a as bothsensors are bed. cooled by the moving slurry. 38 T1Bot increases rapidlyThe sudden bed reduces the heat Flow rate is reduced to create due tohigh heat supply removal from the bottom of the a sudden stationary bed.to the bottom sensor pipe. before flow reduction. The controller reactsto the rapid I.e. heat is stored in the temperature increase and reducessensor. the heat supply accordingly. 39 dW increases and The green LEDchanges to the The bed detection happens passes upwards through yellowLED indicating a bed, while within 1 Minute, which is the threshold. theslurry is still flowing. much faster than the detection of bed erosion,which was about 3 Minutes 53 T2 increases rapidly W2 is reducedautomatically by the Flow rate is stopped to zero. due to stored heat incontroller. the sensing head. 54 W2Top passes The yellow LED changes tothe red T1Bot only reacts mildly to downwards through the LED for NoFlow conclusion. the flow stoppage, as the threshold for ‘Not sensor isalready covered enough Flow’. with a settled bed. 55 The under-swing ofControl parameters and thresholds The correct setting of the two dW doesnot pass are suitably set for this test thresholds is important todownward through the configuration. ensure that during flow thresholdfor no bed. reduction, TH NeF is passed by W2, i.e at 54 minutes inabove test, before dW would potentially passing through TH Bed, i.e. at55 minutes in above test.

We claim:
 1. A method of electronically deriving a conclusion of acondition of slurry flow in a non-vertical conduit having a conduit walland which contains a slurry to flow or flowing along the conduit, themethod comprising: artificially generating at a first heating point onthe conduit wall, which is defined at the invert of the conduit, a firstlocally heated spot on an interior surface of the conduit wall, usingheat delivered to the conduit wall by a first heating device at a firstvariable heating power level W1 that is substantially constant overtime; artificially generating at a second heating point on the conduitwall, which is defined angularly spaced from the first heating point atan angular spacing of at least 90° and which is not spaced from thefirst heating point along the length of the conduit but which lies inthe same cross-sectional plane of the conduit as the first heatingpoint, a second locally heated spot on the interior surface of theconduit wall using heat delivered to the conduit wall by a secondheating device at a second variable heating power level W2 that issubstantially constant over time; locally measuring the temperatures ofthe first and second locally heated spots respectively, therebyobtaining a first temperature value T1 and a second temperature valueT2; measuring, at a predetermined reference point spaced from the firstand second heating points, a third reference temperature value T3;communicating electronically generated signals carrying the values W1,W2, T1, T2, and T3 to one or more electronic computing devices, whichoperatively receive/s the signals and electronically: automaticallycalculate/s a first temperature difference dT1 between T1 and T3 andcompare/s dT1 to a reference value for dT1, being dT1ref, automaticallycause/s the first heating device to change the heating power level W1delivered to the conduit wall at the first heating point if dT1 is notequal to dT1ref, optionally not within an allowable deviation of dT1ref,sufficiently to change T1 such that dT1 is equal to dT1ref, optionallywithin an allowable deviation of dT1ref, automatically calculate/s asecond temperature difference dT2 between T2 and T3 and compares dT2 toa reference value for dT2, being dT2ref automatically cause/s the secondheating device to change the heating power level W2 delivered to theconduit wall at the second heating point if dT2 is not equal to dT2ref,optionally not within an allowable deviation of dT2, sufficiently tochange T2 such that dT2 is equal to dT2ref, optionally within anallowable deviation of dT2ref; automatically calculate/s a powerdifference dW between W1 and W2 and compares dW to a reference value fordW, being dWref, automatically compare/s W2 to a reference value for W2,being W2ref, and automatically derive/s a conclusion of a condition ofslurry flow prevailing in the conduit based at least on a relationshipbetween dW and dWref and between W2 and W2ref, that if an absolute valueof dW is smaller than an absolute value of dWref and an absolute valueof W2 is greater than an absolute value of W2ref, there is unrestrictedflow in the conduit, in that no flow restricting bed of solid materialhas formed at the invert of the conduit, if an absolute value of dW isgreater than an absolute value of dWref and an absolute value of W2 isgreater than an absolute value of W2ref, there is partially restrictedflow in the conduit, in that a flow restricting bed of solid materialhas formed at the invert of the conduit, and if an absolute value of W2is smaller than an absolute value of W2ref, there is restricted flow inthe conduit, in that flow in the conduit has virtually ceased.
 2. Themethod according to claim 1, wherein W2ref>0 W2ref>dWref>0 W2>W2ref atunrestricted flow W1=W2 at unrestricted flow.
 3. A slurry flow conditionmonitoring system for electronically deriving a conclusion of acondition of slurry flow in a non-vertical conduit having a conduit walland which contains a slurry to flow or flowing along the conduit, thesystem including: a first heating device that is arranged and configuredto deliver heat to the conduit wall at a first heating point on theconduit wall, which is defined at the invert of the conduit, therebyartificially to generate a first locally heated spot on an interiorsurface of the conduit wall by delivering heat to the conduit wall at afirst variable heating power level W1 that is substantially constantover time, and a second heating device that is arranged and configuredto deliver heat to the conduit wall at a second heating point on theconduit wall, which is defined angularly spaced from the first heatingpoint at an angular spacing of at least 90° and which is not spaced fromthe first heating point along the length of the conduit but which liesin the same cross-sectional plane of the conduit as the first heatingpoint, thereby artificially to generate a second locally heated spot onan interior surface of the conduit wall by delivering heat to theconduit wall at a second variable heating power level W2 that issubstantially constant over time; first and second temperature sensorsthat are arranged locally and configured to measure the temperatures ofthe first and second heated spots respectively, thereby to obtain afirst temperature value T1 and a second temperature value T2; a thirdtemperature sensor that is arranged and configured to measure a thirdreference temperature at a reference point spaced away from the firstand second heating points, thereby to obtain a third referencetemperature value T3; electronic signal generating means capable ofelectronically generating signals carrying the values W1, W2, T1, T2 andT3; and one or more computing devices in communication with theelectronic signal generating means operatively configured to receive thesignals carrying the values W1, W2, T1, T2 and T3, the one or morecomputing devices being programmed electronically and configured to:automatically calculate a first temperature difference dT1 between T1and T3 and compare dT1 to a reference value for dT1, being dT1ref,automatically cause the first heating device to change the heating powerlevel W1 delivered to the conduit wall at the first heating point if dT1is not equal to dT1ref, optionally not within an allowable deviation ofdT1ref, sufficiently to change T1 such that dT1 is equal to dT1ref,optionally within an allowable deviation of dT1ref, automaticallycalculate a second temperature difference dT2 between T2 and T3 andcompare dT2 to a reference value for dT2, being dT2ref automaticallycause the second heating device to change the heating power level W2delivered to the conduit wall at the second heating point if dT2 is notequal to dT2ref, optionally not within an allowable deviation of dT2,sufficiently to change T2 such that dT2 is equal to dT2ref, optionallywithin an allowable deviation of dT2ref; automatically calculate a powerdifference dW between W1 and W2 and compare dW to a reference value fordW, being dWref, automatically compare W2 to a reference value for W2,being W2ref, and automatically derive a conclusion of a condition ofslurry flow prevailing in the conduit based at least on a relationshipbetween dW and dWref and between W2 and W2ref, that if an absolute valueof dW is smaller than an absolute value of dWref and an absolute valueof W2 is greater than an absolute value of W2ref, there is unrestrictedflow in the conduit, in that no flow restricting bed of solid materialhas formed at the invert of the conduit, if an absolute value of dW isgreater than an absolute value of dWref and an absolute value of W2 isgreater than an absolute value of W2ref, there is partially restrictedflow in the conduit, in that a flow restricting bed of solid materialhas formed at the invert of the conduit, and if an absolute value of W2is smaller than an absolute value of W2ref, there is restricted flow inthe conduit, in that flow in the conduit has virtually ceased.
 4. Thesystem according to claim 3, wherein W2ref>0 W2ref>dWref>0 W2>W2ref atunrestricted flow W1=W2 at unrestricted flow.